Optical fibers are used in a wide variety of applications ranging from telecommunications to medical technology and optical components. Because of their unique structure, optical fibers are capable of highly accurate transmission of light, which is relatively unaffected by interference, diffusion, and other signal de-enhancing phenomena. However, for optical fibers to function at their optimum potential they must be structurally intact and free of scratches, cracks, leaks, or substantially unequal distributed stress.
Optical fibers consist of a core material that is surrounded by a cladding. The difference between the indexes of refraction of the core and cladding materials (which, in some cases, are simply different types of fused silica glass) allows the optical fiber to function. Most commercially available optical fibers, in addition, have an external "buffer or jacket". The jacket is a thin coating (usually plastic, other polymer, or metal) which is applied to the fiber to protect it from being scratched during handling and to limit the amount of water that can come into contact with the fiber. Scratching or contact with water or moisture can deleteriously affect both the optical properties and the strength of the glass fiber. In addition to shielding the fiber's surface, the buffer also operates to help maintain the high tensile strength and the bending capability of the glass optical fibers. A number of fiber optic applications require that one terminus of the fiber be located in an environment isolated from the other terminus. This implies the use of a connector, coupling device, or "feed through" which serves as the point of communication between the distinct environments. Oftentimes, it is necessary or desirable for the point of communication between the environments to be completely sealed except for the presence of the optical fiber. Herein arises the need for a satisfactory method to hermetically seal optical fibers. Further it is desired to provide support for fiber ends to be joined or coupled. Sleeves may also be used to align and support a plurality of fibers. Methods are known for placing and affixing optical fibers in sleeves of different types for the purposes of providing a protective sheath for reducing damage to optical fibers that would otherwise be exposed, and for attempting to provide a housing for optical fibers. In many of these applications an adhesive such as epoxy is placed in the sleeve with the optical fiber to provide a bonded seal between the fiber and the sleeve.
In one U.S. Pat. No. 5,734,767 issued Mar. 31, 1998 in the name of Belt a method of making a hermetically sealed fiber optic coupler comprises at least one optical fiber and a tubular sleeve. The fibers are inserted into the tube and the empty space is filled with an adhesive.
In another U.S. Pat. No. 5,594,822 issued Jan. 14, 1997 in the name of Berkey a method of making a fiber optic coupler comprises a plurality of optical fibers and a sleeve having a circular bore. The fibers are inserted into the tube and the sleeve is then collapsed onto the fibers.
In yet another U.S. Pat. No. 5,754,720 issued May 19, 1998 in the names of Quinn, Robson, Swaroop, Weidman spacer fibers are used to prevent the active optical fibers from sagging or crossing over during the process of collapsing the sleeve onto the fibers. In all these methods, when applied to a plurality of optical fibers, the optical fibers are exposed to substantially unequal distributed stress significantly distorting an optical signal transmitted through the optical fibers.
Therefore, it is an object of this invention to provide a sleeve for retaining a plurality of optical fibers minimizing unequal distributed stress often associated with placing a plurality of optical fibers within a sleeve or ferrule.